Ship



E. V. LEWIS SHIP 3 Sheets-Sheet 1 Filed March 11, 1959 i 0- I /KH 3 GE 7o N w m o HHHHH I I I MH IHH I 1H nu N m m E. V. LEWIS March 14, 1961SHIP 3 Sheets-Sheet 2 Filed March 11, 1959 INVENTOR ATT'oRNEn E. V.LEWIS aha: 43

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-m 0743 43 2 mm N M743 non: QN IS SHIP Edward V. Lewis, Hohokus, N.J.,assignor, by mesne assignments, to the United States of America'asrepresented by the Secretary of the .Navy.

Filed Mar. 11, 1959,'Ser. No. 798,195 Claims. (Cl. 114-'56) Thisinvention generally relates to surface ships for high speed operation,and more particularly relates tosimprovements in hulls for surface shipsin order to obtain greater seaworthiness at high speeds in rough waters.

A surface ship undergoes various undesirable motions, such as roll,pitch, and heave, when traveling in seaways. When these motions areexcessive, they produce destructive forces which have an adverse effecton the structure of the ships hull, on the structural parts andarrangements Within the hull, and on the functioning'of machinery,instruments and other equipment of the ship. In the case of a fullyloaded cargo ship, excessive motions may cause shipping of water in headseas to the detriment of the ships cargo. Furthermore, accelerationsinherent in such motions are believed to be primarily responsible forseasickness and frequently for shipboard accidents. Other undesirableeffects are caused by motions of a ship; and it is not unusual for aship to reduce its speed in order to limit such effects. 7. r

The nature and extent of the motions of'asurface ship depend in partupon the waves that the ship encounters. Thewwaves will be of differentlengths, heights and steepness, and include waves having lengthsofthesame-order of magnitude as thelength of the ship. Under certainconditions of ships speed, a synchronism? arises which magnifies some ofthe motions of .a ship and increases the harmful effects thereof. This,synchronism arises when the natural pitching period of a shipharmonizes with its period of encounter with waves. ,The speed of.aship, when this synchronism arises, is calledthe critical speed of theship. When the speed of the ship is below this critical speed, it isrecognized as operating in asubcritical range, and when above inasupercriticai range. Operating the ship in either range reduces thedeleterious effects of the magnified motions of 'sy'nchronism. I I

An object of the invention is to provide a displacementtype surface shipcapable of operating safely and with small amplitudes of verticalmotions at ,high speeds in both calm and rough sea's, the ship beingcapable ofoperating at supercritical speeds in rough seas when suchoperation. is preferred.

It is a further object of the present invention to provide lines for thehull of a ship that result in .a's'hip having reduced amplitudes ofmotion, safe operating speeds, .especiallyin rough seas, and-otheradvantages.

In'ge'neral, it is an objectof the invention to provide a surface shipof high speed having a long natural pitching period.

Other objects and many of the attendant advantages of this inventionwill'be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with theaccompanying drawings in Whi'ch' like reference im-2,974,624 Patented Mar. 14, 196i ICE meralsdesignate like partsthroughout the figures thereof and wherein:

Figs. 1A and 13, joined along the broken lines, is a longitudinalelevational outline view of a ship having a hull in accordance with theinvention;

Figs. 2A and2B, joined along the broken line, 'is a diagram showing, inaccordance with standard practice, a half-plan view of thelongitu'dinalwater lines of the hull at different water line planar levels;

Fig. 3 is a diagram showing, in accordance with standard practice, abody plan of the transervsehull lines or cross-sections at variousstations, the lines on the right of the center line being forward orforebody lines at different stations, and the lines on the left of thecenter line being the aft or afterbody lines at different stations.

A ship in'accordance with the invention is built with a hull along thelines of Figs. 1-3. Figs. 1A and 1B, the top line A represents the maindeck and the bottom line B represents the base line of the hull, and maybe considered indicative of its keel. The ship has a bow C and thesternD. In Figs. 2A and 2B the line E represents the and comparatively highervertical longitudinal center plane of the hull, it being understood thatthe hull is symmetrical on both sides of this plane. Foridentificationpurposes, the length of the ship is divided into spacedtransverse stations. Generally the practice is to divide the ship intotwenty stations, each station representing a plane that is perpendicularto the longitudinal axis of the hull. The stations shown in Figs. 2A and2B are the even stations ()(zero) through 20, but with the addition of acentral station '11. The stations are equally spaced except thatstations 10 and 1 1 and stations 11 and 12 have somewhat smaller spacestherebetween, the two spaces, however, being equal.

Similarly, as shown in Fig. 3, the vertical extent of the hull isdivided by spaced horizontal water line planes shown as lines (WLP) 2,4, 6, 8, 12, 13, 14, 16. 17, 18, 20, 22 and 24 which are relativelyspaced from the base line in the ratios indicated in the associatedparentheses.

The figures are drawn substantially to scale, but not necessarily tothesame scale. In Figs. 1A and 1B, the ver tical scale is double thehorizontal (fore and aft) scale. In Figs. 2A and 2B, the vertical scaleis three times the horizontal scale. This has been done in order betterto show the configuration of the water line projections which, if drawnto the same scale throughout, would re.- quire the lines to be moreclosely spaced than shown in the figure. In .Fig. 3, the horizontal andvertical scales are the same.

The transverse station planes and the water line planes intersect thehull in curved lines which are indicated in Figs. 2A, 2B and 3 inaccordance with standard practice,

each line being identified with the plane in which it lies. In Figs. 2Aand 2B these curved lines are the lines including the designation WL;and in Fig. 3 they are the lines including the designation T.

An inspection of Figs. 2A, 2B, and 3 shows that the hull forms alongslender ship with very fine water lines that is adapted for destroyertype vessels. The ship shown has a length to beam ratio of 10.5.

'It is difiicult to describe the shape of the hull in a few words. Asindicated in Figs. 2A and 23, between the transverse central stations 16and 12, which may be called them'idship of the hull, the hull is offairly uniform width, except at the bilge and below the water line. Thedistance between stations 10 and 12 represents 13.3 percent of thelength of the ship. The distance forward of station to the zero stationrepresents 48.2 percent of the length of the ship. I

Forwardly of station 10, the water lines converge longitudinally fairlysmoothly to the bow stem, but with the upper and the lowermost linessomewhat more rapidly than the central longitudinal lines WL4 throughWL13. Rearwardly or aft of station 12, the bottom rises relativelyrapidly to a knuckle near water line plane WLPlll. The upper abaft waterlines converge longitudinally and more rapidly than the forward waterlines.

Transversely, the upper midship portion between stations 10 and 12 hasfairly straight walls with slight tumble home near the top. Fore and aftof midship portion, the hull has significant tumble home. This isapparent from Figs. 2 and 3. The water line plane WLP13 forms the waterline of the ship under normal operation. This line is only slightlyabove the vertical center water line plane of the hull which is exactlymidway between the deck and base line; and the tumble home above WLP13is appreciable both fore and aft of the midship portion. This isapparent in Fig. 3 from the large inward curving of lines T2, T4, T6 andT8 of the morebody, and lines T14, T16, T18 and T20 of the afterbody.The inward curvature of these lines starts from below WLP13, the normalwater line plane, and extends almost to the deck, WLP24.

As is apparent from Figs. 2A, 2B and 3, the hull is shaped somewhat likea submarine, except for the uppermost part which is bounded by the maindeck at the water line plane WLP24. The reason for this is to permit theship to ride lower in the water when it encounters rough seas. Waterline plane WLP17, called the submerging Water line plane forconvenience, represents the water line for the ship operating in suchseas. This last line is about three-fourths of the height of the hullabove the base line. When riding thus, the ship resembles a surfacedsubmarine but is considerably longer and more slender.

In order to lower the ship to the submerging water line plane, therebyincreasing the displacement, the ship is provided with peak waterballast tanks fore andaft, and with flooding and pumping equipment tofill and empty the tanks. Preferably the heavier moving parts of thisequipment are in the midsection of the ship. The tanks and equipment,per se, form no part of the invention, since any suitable apparatus maybe used. Accordingly, they have been schematically indicated in Figs. 1Aand 1B as comprising tanks 50 and 52, and pumping equipment 54.

It will be observed in Figs. 2A and 2B that the ship has a narrow maindeck indicated by water line WL24, and that the submerging water linearea encompassed by the WL17 is also narrow but not as narrow as thedeck.

2e ship has a low freeboard above the water line plane In calm weather,the ship floats at the normal water line shown. Under storm conditions,the ballast tanks are filled until the ship settles so as to be at thehigher submerging water line. The result is an increase in the naturalpitching period of the ship arising from the increased mass, radius ofgyration, and decreased waterplane area. The location of the ballast atthe peaks of the hull also lengthens the natural pitching period.

The increased pitching period of the ship induces the ship to plungethrough waves rather than riding over them. The ship can then operate atsupercritical speeds with acceptable seaworthiness. A lengthened andfine ship of a type described with lengthened pitching period permitsoperation in storm seas at speeds as much as fifty percent higher thanships of customary design such as the aforesaid destroyer.

The high speed operation in rough seas and the low freeboard subject theship to boarding seas. Consequently, the ship must be structurallystrong, with the main deck heavily built. The size of 4 deck,represented by numeral 56 in Figs. 1A and 1B, is kept to a minimum, withadejuate strength to withstand the boarding water.

Because of the rounded sides of the ship, it is prone to rolling motion.For reduction of this motion, antirolling fins may be provided on thehull.

The improved characteritics of a ship in accordance with the inventionis apparent from the following data given in unit ratios unlessotherwise indicated.

Semi-submerged Ship at deep draft Destroyer (WLP17 Length of LWL 5.7205.720 Breadth 0.608 0.540 Draft 0.208 0.250 Displacement, pound units24.5 27.7 Freeboard at bow, F 0.280 0.100 Freeboard ratio, F/L (Length)0.049 0.017 Longitudinal radius of gyration 0.24L 0.26L Natural pitchingperiod, T,,, sec 0.60 0.92 r,,/ vi 0.25 0.38

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

I claim:

1. A surface ship adapted for high speed operation in rough seas whiletraveling in a semi-submerged condition, comprising a hull having anormal operation water line substantially midway of the height thereof,said hull having a midship portion with substantially straight sidesabove said water line, the portion of said hull forward of said midshipportion having a deck having a lesser area than the area of a planethrough said water line, the portion of said hull forward of saidmidship portion being longer than the portion of said hull aft of saidmidship portion, said forward and said aft portions having tumble homelines, the forward portion comprising about 48.2 percent of the shipslength, and the midship portion about 13.3 percent of the ships length,said forward portion converging to the bow stern, and said rearwardportion converging to a knuckle line at the stern, the bottom, exteriorof said hull being outwardly curved from said water line to its' keel,said ship having peak ballast tanks adapted when filled to place thewater line a distance about threefourths of the height of the hull aboveits base line, a plane through the last said waterline being of lesserarea than the area of the plane through the first said water line, butof greater area than said deck.

2. A surface ship adapted for high speed operation in face thereof overat least a portion of the area thereof.

4. A surface ship adapted for high speed operation in rough seas whiletraveling in a semi-submerged condition, as set forth in claim 1wherein, the exterior surface of said hull both forward and aft of themidship portion, and above said second waterline, is inwardly curved.

5. A surface ship adapted for high speed operation in rough seas whiletraveling in a semi-submerged condition, as set forth in claim 1wherein, the exterior surface of the forward portion of the hull locatedbetween the first andsecond waterlines is composed at least in part, ofan area that is outwardly curved at the exterior surface, and

the structure above the 15 a portion that is inwardly curved at saidexterior surface,

and is inwardly curved above said second waterline; and References Citedin the file of this patent the portion of said hull aft of said mishipportion and 10- UNITED STATES PATENTS cated between said first andsecond waterlines has substan- 293 793 sebiuot Feb. 19 1884 tially theentire exterior surface thereof outwardly curved, 768269 Aug 1904 andsaid exterior surface of said aft portion of the hull 5 2185:431 Burgessf Jam 1940 located above said second waterline inwardly curved. 72,253,245 Norton et a1 Aug 19, 1941

